Sell Your Books on Amazon.com
A quick, fun and easy way to score extra cash is to sell your books on Amazon.com. Click the "sell your stuff" link on the site, enter the ISBN of your book, answer a couple of questions about its condition and set a price. I always price mine just below the lowest listed price, so the listing will go to the top of the list.
Just recently, I listed Freakanomics and Widow of the South after my husband and I purchased and read them ... We got $20 for them and they sold within hours of the posting.